Process for the preparation of 3-(3&#39;-lower carboalkoxy-4&#39;-hydroxy-1&#39;-naphthyl)-3-(3&#34;-carboxy-4&#34;hydroxy-1&#34;-naphthyl)naphthalide

ABSTRACT

Carboxy-substituted 1-naphthol naphthalide indicator dyes are prepared by a base-catalyzed reaction of a 2-carboxy-1-naphthol and a 3-Z-3-(3&#39;&#39;-lower carboalkoxy-4&#39;&#39;-hydroxy-1&#39;&#39;naphthyl)naphthalide wherein Z is a leaving group to form the dye precursor which is then hydrolyzed to yield the corresponding indicator dye product.

United States Patent Huyffer et al.

[11] 3,821,254 June 28, 1974 PROCESS FOR THE PREPARATION OF 3-(3'-LOWERI CARBOALKOXY-4 -HYDROXY- I NAPHTHYL )-3-( 3 CARBOXY- 4' 'HYDROXY-l'-NAPH THYL)NAPHTHA- LlDE [75] Inventors: Paul S. Huyffer, West Boxford;John J. Wasatonic, Cambridge, both of Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

- I Mass. 22 Filed: Dec.ll, 1972 [2]] Appl. No.: 314,096

52 us. (:1 .Q ..260/343.2R

51 nt. Cl C07d 7/10 [58] Field of Search 260/3432 R [57] ABSTRACT.Carboxy-substituted l-naphthol naphthalide indicator dyes are preparedby a base-catalyzed reaction of a 2-carboxy-l-naphthol and a3-Z-3-(3'-lower carboalk- 0xy-4'-hydroxy--l-naphthyl)naphthalide whereinZ is a leaving group to form the dye precursor which is then hydrolyzedto yield the corresponding indicator dye product.

9 Claims, No Drawings PROCESS FOR THE PREPARATION OF 3-(3-LOWERCARBOALKOXY-4-HYDROXY- 1 '-NAPHTHYL)-3-(3' '-CARBOXY-4' 'HYDROXY- I'-NAPHTHYL)-NAPHTHALIDE BACKGROUND OF THE INVENTION l. Field of theInvention This inventionrelates to a method of preparing naphthalideindicator dyes, and in particular, it relates to the synthesis ofcertain l-naphthol naphthalides useful as.

reagents in photography.

2. Description of the Prior Art of a catalyst.

Copending US. Patent application Ser. No. 103,865

of Myron S. Simon filed Jan. 4, 197] discloses and claims certainindicator dyes derived from l-naphthols which find particular utility asoptical filter agents in photographic processes for protecting anexposed photosensitive material from post-exposure fogging duringdevelopment in the presence of incident light. Specifically, thel-naphthol indicator dyes disclosed therein comprise 3,3-disubstitutedphthalides and naphthalides wherein 'the 3,3 substituents are4-hydroxy-l naphthyl radicals at least one and preferably both of whichpossess a hydrogen-bonding group, such as, a

carboxy, hydroxy, sulfonamido or sulfamoyl group substituted on a carbonatom adjacent to the 4'-hydroxy group. Among such dyes are phthalidesand naphthalides wherein one or both of the 4'-hydroxy-lnaphthalide or adiester of the 3-hydroxy naphthalide to form the dye precursor followedby hydrolysis to yield the indicator dye product. Depending upon theparticular naphthalide intermediate, these prior meth-- ods haveemployed an acid, such as, aLewis acid or a heavy metal salt, such as,silver tetrafluoroborate to catalyze the reaction of the l-naphthol andintermediate, or the reaction has been conducted in the absence Thepresent invention is concerned with another mest ata".

thod of synthesizing the aforementioned carboxynaphthol naphthalide dyeswhich comprises a basecatalyzed reaction to yield the dye precursor.

SUMMARY OF THE INVENTION It is, therefore, the primary object of thepresent invention to provide a method of synthesizing lnaphtholnaphthalide indicator dyes.

Other objects of this invention will in part be obvious a l mwry ar Pameter-Mt..-

The invention accordingly comprises the processes involvingthe severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the products andcompositionspossessing thefeatures, properties and the relation of elements whichare exemplified in the following detailed disclosure, and the scope ofthe application of which will be indicated in the claim.

According to the present invention, carboxysubstjtuted l-naphtholnaphthalides are synthesized by condensing (a) a 2-carboxy-l-naphtholand (b) an intermediate, 3-Z-3-(3lowercarboalkoxy-4'-hydroxyl'-naphthyl)naphthalide wherein Z is a leavinggroup, in the presence of a catalytic amount of base to yield thecorresponding dye precursor. The lower carboalkoxy group of the dyeprecursor is then converted to a carboxy group to yield thecorresponding dye product.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

I present invention comprises:

.zsaasstst..-

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found quiteunexpectedly that bases having a pKa of not less than about 2 which arenon-water producing in thereaction of a l-naphthol and a naphthalideintermediate may be used to catalyze the condensation ofZ-carboxy-l-naphthol and a dye interme diate, 3-Z-3( 3'-lowercarboalkoxy-4-hydroxyl -naphthyl)naphthalide wherein Z is a leavinggroup, for ex- Specifically, the method of preparing carboxysubstitutedl--naphthol naphthalides-according to the A. reacting (a) a3-Z-3(3-lower carboalkoxy-4- hydroxy-l -naphthly)naphthalide wherein Zis a leaving group and (b) a Z-carboxy-l-naphthol, unsubstituted orsubstituted with an aliphatic group in a molar ratio of about 1.0-1.5:1in inert organic solution at a temperature not exceeding about C. in thepresence of a catalytic amount of a non-water producing base having apKa of not less than about 2 to form the corresponding 3-( 3-lowercarboalkoxy-4-'-hydroxy-l naphthyl)-3-( 3-carboxy-4"-hydroxyl -naphthylnaphthalide dye precursor and I B. hydrolyzing said dye precursor toform the corresponding 3-(3'-carboxy-4'-hydroxy-l -naphthyl )-3- (3-carboxy-4 '-hydroxy-l -naphthyl )naphthalide The method of the presentinvention is shown in the following reaction sequence as illustrated bya mono- ,flhsri ts ms ats where Z, is 0 COzMe HOOC o 1201 To H 0H 0 l ll 001MB HOOC- Y K/ Y base (B) OH on ([311 on COzMo Hooo- 00H HOOC- Y YK/ hydrolysis K/ Though the method of the present invention may be usedin the synthesis of l-naphthol naphthalides, in general, it findsparticular utility in the synthesis of indicator dyes as represented bythe formula:

( oH (I COOH HOOC wherein Y is hydrogen or an aliphatic ,group usually,

containing up to about 20 carbon atoms.

The aliphatic group, branched or straight chain, may be alkyl, suchas'methyl, ethyl, isopropyl, butyl, t-butyl, hexyl, dodecyl, octadecylor eicosanyl; alkenyl, such as, 3-butenyl, 2-methyl-l,3-butadienyl,2-hexenyl and 9- octadecenyl; alkoxy, such as, ethoxy, butoxy,1-ethoxy-2-(,B-ethoxyethoxy), hexyloxy, dodecyloxy, and octadecyloxy;and alkoxyalkyl, such as, methoxyethyl, methoxyethoxyethyl,butoxydodecyl and ethoxyethoxyhexadecyl. Also, the aliphatic group maybe substituted with a solubilizing group, i.e., the alkyl, alkenyl,alkoxy and alkoxyalkyl groups enumerated above may be substituted with asolubilizing group, e.g., -OH, -COOH and -SO H.

- Specific examples of l-naphthol indicator dyes that may be preparedaccording to the method of the present invention are as follows: v

OH OH HOOC COOH COOH HOOC OH OH coon HOOC COOH HOOC

erentially between about 0.05 and 0.15 mole per 1.0

mole of Z-carboxyl-naphthol.

In carrying out the method of the present invention, 7

I aqueousorganicsolution, for example alcohols, such as Useful as thecatalyst are all bases strong enough to form salts with the naphtholcarboxylic acid, i.e., 2-carboxy-l'naphthol present .in the reactionincluding weaker bases having a pKa down to but not less than about 2,all of which are capable of forming salts with the naphthol carboxylicacid to some extent. Also, because the intermediates tend to besensitive to moisture, the base selected to catalyze the reaction shouldnot produce or release water during the reaction. Other than inorganicoxides and hydroxides and other bases that would form water, any basehaving a pKa of not less thanabout'Z, including both organic andinorganic materials may be employed. Illustrative bases that may be usedas the catalyst include inorganic bases, such as, lithium, sodium andpotassium hydrides or amides, and organic bases, for example, primary,secondary and tertiary aliphatic amines, such as, n-declylamine,di-nbutylamine, triethylamine, n-butylamine', diisopropylamine,piperazines, piperidines, morpholines and aromaticamines, such as,aniline, 4-bromoaniline, N,N- diethylaniline, p-toluidine,N-methylaniline. Particularly useful catalysts are aromaticN-heterocyclic bases,

such as, pyridines, picolines, lutidines, pyrimidines, pyridazines,pyrazines, imidazoles and quinolines. Preferred catalysts are thepyridines including pyridine and pyridine substituted with, for example,hydroxy, amino, halo, lower alkoxy: and lower alkyl.

As the reaction media, any inert organic liquid that ethanol, methanol,isopropanol, or water miscible ethers, for example,1,-2-diinethdxyethane or tetrahydrofuran.

Though the dye precursor isolated from the reaction solution may behydrolyzed directly to the corresponding indicator dye product, it maybe purified, for example, by crystallization of the crude material in anappropriate solvent-prior to the hydrolysis step. Suitable solventsinclude alcohols, such as, isopropanol; combinations of alcohols withchlorinated hydrocarbons, such as, isopropanol and methylene chloridemixture; or with ketones, such as, methanol and acetone mixture; andcombinations of nitriles with ethers, esters, ketones or hydrocarbons,such as, mixtures of acetonitrile with dimethoxyethane, n-butyl formate,methyl ethyl ketone is a solvent for the reactants may be employed.Suitable organic solvents include acetonitrile, methyl ethyl ketone,hexane, 1,4-dioxane, tetrahydrofuran, benzene, toluene, xylene,cyclohexane, methylene chloride, t-

butanol, dimethoxyethane, dimethylsulfoxide andv N imst ylf mam d Forachieving practical reaction times, the reaction is conducted atelevated temperatures. However, to

prevent decarboxylation of the naphthol reactant, the temperature shouldnot exceed about 85C., andusually, the reaction temperature rangesbetween about 60 and 85C.

Because of the moisture sensitivity of the naphthalide intermediates,the condensation should be conducted under substantially anhydrousconditions, and though not essential, the reaction is preferablyconducted under an inert atmosphere, for example, nitrogen.

The dye precursor tube obtained may be hydrolyzed, for example, bytreating with an alkaline hydroxide in aqueous or aqueous-organicsolution to convert the 3'- carboalkoxy to a 3'-carboxy group to yieldthe desired indicator dye product. The alkaline hydroxide may beanalkaline earth hydroxide, such as calcium or barium hydroxide, orpreferably, an alkali metal hydroxide,

such as, sodium or potassium hydroxide. Any water-,

miscible organic liquid may be used to form the or benzene.

The Z-carboxy-l-naphthols employed in the subject method may berepresented by the formula:

(II) OH wherein Y has the same meaning given in formula I I above.

Among the'naphthols which are particularly useful'in the production ofindicator dyes that are relatively or substantially immobile in a givensolutionare the alkoxysubstituted 2-carboxy-l-naphthols which form thesubject matter of copending U.S. Patent application Ser. No. l74,'l7l ofRichard B. Greenwald filed Aug.

naphthols also may be prepared by treating a 1,6- or l,7-naphthalenediolin solution in an aprotic solvent with carbon dioxide in the presence ofa strong base to form the corresponding 2-carboxy compound which is thenreacted with an alkyl halide to yield the alkoxysubstituted 2-carb oxyl-naphthol.

The naphthalide intermediates employed in the subi st -mstl qd.ms xl srep nt th qrmyl i (III) 0H OOR" wherein R" islower alkyl, e.g., ethyl,propyl, isopropyl, n-butyl, t-butyl and preferably, methyl and Z is aleaving group. Typical leaving groups are halo, -OR wherein R is amonovalent hydrocarbon radical or a monovalent substituted hydrocarbonradical and The halo intermediates may be prepared by halogenation of a3-hydroxy-3-(3'-lower carboalkoxy-4- hydroxyl -naphthyl)naphthalide tothe corresponding 3-halo naphthalide, preferably, 3-chloro or 3-bromo.This may be accomplished by treating the 3-hydroxy naphthalide withphosphorus 'pentachloride, thionyl chloride, phosphorus pentachloride,N- chlorosuccinimide, phosphorus oxychloride, sulfuryl chloride,phosphorus tribormide, N- bromosuccinimide, aluminum bromide, chloride,boron tribromide, N-bromocaprolactam, cupric bromide or otherconventional chlorination or bromination reagent.

The monoether intermediates, 3-OR, may be synthesized by reacting a3-hal0 naphthalide, for example, a 3-chloro-3-( 3-'-lowercarboalkoxy-4'-hydroxy-l naphthyl) naphthalide and a monoor polyhydricaromatic or aliphatic alcohol, saturated or unsaturated, branched orstraight chain, such as, benzyl alcohol, ,B-phenylethyl alcohol,'yphenyl-n-propyl alcohol, cinnamyl alcohol, methanol, ethanol,isopropariol, secbutanol, tert-butanol, l-octanol, 1,2-ethanediol, 1,3-propanediol, l ,4-butanediol, l ,2,3-prop anetriol, ethenol,2-propenel-ol 3-butenel -o 1; or by reacting a 3-halo naphthalide and aphenolic compound, such as, a-naphthol, ,B-naphthol,1,6-naphthalenediol, 1,7-

naphthalenediol, phenol, catechol, resorcinol, hydroquinone, pyrogalloland phloroglucinol. The alcohol or phenolic compound may beunsubstituted or substituted with one or more groups, e.g., halo, cyano,carboxy, nitro, acetyl, lower alkyl and lower alkoxy. The monoetherintermediates derived from aliphaticor aromaticalcohols also may beprepared by reacting the alcohol with a 3-hydroxy-3-(3'-lowercarboalkoxy-4- hydroxy-l -naphthyl)naphthalide. Monoether intermediatesof phenols also may be prepared by reacting a 3-( 3 -lowercarboalkoxy-4'-hydroxy-l '-naphth yl naphthalide with a quinone, suchas, oor p -chloranil or 2,3-dichloro-5,6-dicyano-l ,4-benzoquinone. In aparticularly preferred embodiment, the monoether intermediate .is i a3-OR-3-(3-lower carboalkoxy-4-hydroxyl -naphthyl )naphthalide wherein Ris a phenyl group, unsubstituted or substituted with one or more of thesubstitutents enumerated above.

The monoester intermediates,

oxo-l '-naphthylidene)naphthalide and an organic carboxylic acidaccording to the method of copending U.

S. Patent application Ser. No. 314,095 of Michael H. 60

Feingold also filed Dec. 1 l, 1972. The 3-OCOR' of the monoesterintermediate may be derived from an or-. ganic di-' ormonocarboxylicacid, aromatic or aliphatic including branched or straightchain saturated or unsaturated aliphatic acids, such as, benzoic acid,phthalic acid, isophthalic acid, cinnamic acid, a-naphthoic acid,

B-naphthoic, acid, acetic acid, butyric acid, caproic aluminum wherein Ris an alkyl group containing l to 10 carbon atoms, particularlyunsubstituted and monosubstitutedalkyl derived from a saturatedaliphatic monocarboxylic acid, 'COOH.

The latter intermediates have been found particularly useful in thebase-catalyzed reaction with a 2-carboxyll-naphthol to form thecorresponding dye precursor. Because they exist in substantiallycomplete equilibrium with the corresponding dehydro-naphthalideintermediate and undergo highly reversible side reactions,higher'conversions to dye precursor may be achieved with a' minimum ofby-product formation.

The preparation of carboxy-substituted l-naphthol naphthalides employingmonester intermediates for reaction with a Z-carboxy-l-naphthol in thepresence of base is claimed in copending U. S. Patent application Ser.No. 314,097 of Yunn H. Chiang and John W. Sparks filed concurrentlyherewith.

The following examples are given to further illustrate the presentinvention but are not intended to limit the scope thereof.

EXAMPLE 1 The intermediate,

(50 g., 0.08m) and 2-carboxy-6-octadecyloxy-lnaphthol (36.3 g., 0.08 m)were added to a mixture of 680 ml. of tetrahydrofuran, 120 ml. ofN,N-dimethylformamide and 0.87 g. of pyridine (0.01 lm). The mixture wasrefluxed with stirring on a steambath for 24 hours. Initially, theintermediate was only partially soluble but after 8 hours, completesolution was attained. Thin layer chromatography benzene 20 methanol onQuanta silica plates) indicated complete absence of the startingintermediate after 24 hours. The reaction mixture was cooled and pouredinto a mixture of 3.1 of ice and 4 l. of acetic acid with stirring. Thewhite solid was filtered, washed with water and dried at 50C. in avacuum oven.

The dried solid was then stirred in 700 ml. of methylene chloride for30minutesQThe mixture was then filtered through celite and thecake washedwith 700 ml. of methylene chloride. The methylene chloride was distilledoff at atmospheric pressure until the remaining volume was 300 ml. Atthis time 250 ml, of isopropanol was added and the distillationcontinued until the distillate temperature was 78C. The remaining 250ml. of solution was allowed to stand overnight at room temperature.Scratching was needed to induce crystallization and after 2 additionalhours, the white solid was filteredoff and washed with 400 ml. ofisopropanol, 400 ml. of methanol and then dried to give 37.5 g. (56.5percent by weight) of 3-'(3'-carboalkoxy-4- hydroxy-l -naphthyl )-3-( 3-carboxy'4'-hydroxy-6 octadecyloxy-l '-naphthyl )naphthalide dyeprecursor.

The naphthalide dye precursor was hydrolyzed by adding 30.0 g. ofprecursor to a solution containing 200 ml. of water, ml. of isopropanoland 20 mls. of 50 percent by weight aqueous sodium hydroxide and heatingthe resulting solution at reflux (about 82C.) for I two hours. Aftercooling to C., the solution was neutralizedby slowly adding withstirring to an ice-water mixture containing 600 mls. of water, 66.0 g.of 4N hydrochloric acid, 66.0 g. of glacial acetic acid and 1.4

kg. ice. The white solid obtained was filtered and re-'- slurried withwater and then'collected by filtration.

' The solid comprising crude 3-(3-carboxy-4'- hydroxyl '-naphthyl-3-( 3-carboxy-4"-hydroxy-6 octadecyloxy-l -naphthyl)naphthalide dye productwas added to about 300 mls. of methanol with stirring, and the slurrywas heated to reflux at about 2C. per minute. When a steady reflux wasachieved, the slurry was cooled-to 25C., filtered, and the'filter cakewashed with several 30 ml. portions of methanol until the filtrate wasclear. The white solid obtained was then dried at 60C. full vacuum to aconstant weight to give an overall yield of 37 percent by weight oftitle compound.

Amax =648, e=37,300.

The monoether intermediate employed above was prepared as follows:

3-( 3-carbomethoxy-4-hydroxy-l -naphthy1) n aphthalide (85.5 g.; 0.22 m)and o-chlor ani1 (57.0 g.; 0.23m) were added to 1,200 ml. of toluene.The mixture was stirred at reflux for 3 hours. After cooling to roomtemperature, the pinkish solid was filtered and washed with 1500 ofcoldtoluene. The solid was dried EXAMPLE 2 Preparation of the compound offormula (4).

The intermediate, (16.7 g.; 0.04 mole) was slurried in approximately 100.ml. of benzene. Addition of 3.2 g. of pyridine caused immediateformation of a red crystalline sub stance.2-carboxy-6-octadecyloxy-1-naphthol (18.2

-COO CH3 g.; 0.04v mole) was added, and the mixture was heated red"color disappeared, and a solution was obtained.

The solvent was removed in vacuo at 50C., and 100 ml. of water, 100 ml.of ethanol and 25 ml. of 50 percent by weight aqueous sodium-hydroxidewere added.

The resulting solution was heated on a steam bath for about minutes,cooled to' room temperature and added dropwise to acrushed"ice-concentrated hydro- Dry l-hydroxy-Z-naphthoic acid (SO gms.,0.266:

mole) was suspended in 350 ml. dry benzene in a flame-dried 1 liter1-neckround bottom flask under an air condenser and drying tube. Thionylchloride (31.7

- gms., 0.266 mole) was added in one portion followed by 1.5 ml. dryN,N-dimethyl-.formamide. The reaction mixture was'stirred magnetically2-3 days at room temperature. Insoluble material (6.5 gms.) was removedby filtration, andthe yellow-tan filtrate was evaporated to dryness togive pale yellow l-hydroxy-2-naphthoyl chloride, m. p. 8788C. Chilledanhydrousmethanol ml.) was added quickly to the solid chloride in anexothermic reaction. The partialsolution was heated about 5 minutes onthe steam bath under a drying tube then allowed to cool. The suspensionwas chilled and the solid was collected to give 43. gms. (92 percent byweight) of l-hydroxy-Z-fmethyl naphthoate.

A mixture of 6.7 g.'(0.03315 moles) of 1 -hydroxy-2- methylnaphthoateand 6.63 g. (0.03315 moles) of 'naphthalaldehydic acid in 90 ml. 12percent p-toluenesulfonic acid in acetic acid was stirred and refluxedovernight. The 'mixture was then cooled to room tem perature. The solidwas filtered, washed with acetic acid, then water, and dried. The solidthus obtained was recrystallized from 1.400 ml. acetone and 200 ml.methanol (Norit) to give 1 l g. (85 percent by weight) of 3-( 3-carbomethoxy-4 '-hydroxy- 1 '-naphthy1)naphthalide as white hairlikeneedles.

A mixture of the naphthalide prepared above 600 g. (1.56 moles), ando-chloranil, 400 g. (1.63 moles) in' 12,000 m1. dioxane, containing 188g. (3.12 moles) acetic acid, was stirred and refluxed for 17 hours. Atthis point, 50 ml. water was added, and stirring and refluxing wascontinued for an additional 3 hours. The

dark solution .was then evaporated in vacuo to dryness. The residue wastriturated well with ether, and the solid was filtered and washed'wellwith ether, to give 432 g. (69 percent by weight)carbomethoxy-4'-hydroxy- 1 '-naphthyl)naphthalide.

of 3-hydroxy-3-(3'- The 3-hydroxy-3-( 3 -carbomethoxy-4'-hydroxy- 1naphthyl) naphthalide-l,8 (50 gms. 0.125 mole) was suspended in drybenzene (500 ml.) in a flame-dried 1 liter round bottom flask fittedwith a magnetic stirrer and calcium sulfate drying tube. Thionylchloride 16.4 gms., 0.137 mole) was added in one portion followed by 2.5m1. of dry N,N-dimethylformarnide. The suspension was stirred at roomtemperature for 1 day. The 3- chloro-3( 3-carbomethoxy-4'-hydroxynaphthyl) naphthalide-l,8 product was collectedon a Buchner funnel and washed with a small amount of dry hexane.Residual solvent was removed in a vacuum dessicator.

EXAMPLE 3 Preparation of the compound of formula (4).

the intermediate employed in this example was a monoester, manely, themonoacetate having the following formula:

1 To a 300 ml. 3'-neck flask equipped with mechanical stirrer, nitrogenatomsphere and a 20 mLDean- Stark trap was added 150 ml. benzene. Thebenzene was refluxed at least 30 min. to dry the solvent, and theapparatus, the trap removing 25 ml. from the initial solvent volume.After the benzene had cooled to 25C., 9.12 g. (0.02 mole) of2-carboxy-6-octadecyloxy-l naphthol, 10.6 g. (0.024 mole) of the abovemonoacetate intermediate and pyridine, 0.080 ml. 1.0 m. mole) were addedin sequence. The mixture was heated to reflux over a min. interval withrapid stirring and maintained at reflux for 3 hours. At this point, theapparatus was converted to downward distillation, and most of thebenzene, originally 125 ml., was stripped at atmospheric pressure. Atotal of 83 ml. was removed allowing 42 ml. of benzene to remain in thereaction mixture, an easily stirred slurry. (Based on the solid obtainedby complete stripping of benzene from the slurry, conversion to dyeprecursor was 92 percent by weight based on the Z-carboxy-l-naphthol andpurity was 85 percent by weight).

(2) Acetonitrile, 100 ml., was added causing nearly total precipitationof product and the solvent mixture was distilled without fractionation.After 100 ml. was collected, b.p. 75-79C., a second 100 ml. portion ofacetonitrile was added and another 100 ml. of solvent was collected(b.p. 79-8 1C.). Anindex of refraction check of the distillate (boilingat 81C.) revealed pure acetonitrile, confirming the almost completeremoval of the benzene. The reaction slurry, containing 42 ml.acetonitrile as solvent, was treated with 96 ml. butyl formate andbrought to reflux to complete solution. A final portion, 22 ml., ofacetonitrile was carefully added to bring the solvent combination to60:40 butyl formate: acetonitrile. The solution was cooled to 50 C. in30 minutes and to 25C. during the next hour.. Crystals started appearingabove 60C. The mixture was stirred at 25C. for 10-18 hours. The granularsolid was filtered and twice reslurried for 20 min. in fresh ml.portions of acetonitrile. After drying in vacuo at 60C., the productcomprising dye precursor weighed 13.76 g.(82 percent by weight) and wasanalyzed as 97+ percent pure by visible absorption in ethanolic sodiumhydroxide.

(3) A solution of 6.71 g. (8 m moles) of dye precursor obtained above in56 ml. isopropanol was prepared by heating the mixture to reflux. Asolution of 7.68 g. of 50 percent aqueous sodium hydroxide (96 m. moles)in 88 ml water was added over 5 minutes and the resulting solution wasrefluxed under nitrogen for 2 hours. After the heat was removed, aceticacid, 6.4 ml.- (104 m. moles) was added over one minute and the clearyellow solution was cooled and filtered (from potential solidcontaminants). Dropwise addition over 25 minutes to a stirring mixtureof 500 ml. ice water, ml. acetic acid and 20 ml. concentratedhydrochloric acid produced a white solid which was filtered, washed withwater, and vacuum dried at 60C. The off-white solid comprising dyeproduct weighed 6.58 g. and had a visible absorption 6 (648 nm.) 36.1 X10", indicating 97 percent purity. The overall yield of dye at thisstage was 82 percent by weight based on the carboxy-naphthol startingmaterial. I

(4) Exactly 6.00 g; of powdered 97 percent pure dye product and 60 ml.methanol were heated under nitrogen to reflux, over 15 minutes, withrapid stirring, and held at reflux for 30 minutes.

ulc slurry was allowed to air cool with stirring and kept at 25C. for 1A hours- Addition of 20 ml. methanol and stirring for two minutesthinned the thick slurry. The white solid was filtered, washed with 35ml. methanol and vacuum dried at 60C. The yield of final dye having avisible absorption e (648 nm.) 37.1 X 10 (Standard 37.1 X 10 was 5.57 g.(93 percent by weight). This represents an overall yield of titlecompound of 76 percent by weight based on 2- carboxy-6-octadecyloxyl-naphthol.

1n the above procedure, the dye precursor formed in step 1 may beisolated by complete removal of the benzene and hydrolyzed directlywithout purification. To facilitate final purification of the dyeproduct, however, the dye precursor usually is purified prior to thehydrolysis step by crystallization from an appropriate solvent, forexample, methyl ethyl ketone or dimethoxyethane combined withacetonitrile. Alcohols such as isopropanol or 2-butanol may also beused. Particularly preferred as the crystallization solvent is 60:40butyl formate: acetonitrile, since this system gives high recovery(80-82 percent) of highly pure precursor (96+ percent) in a singlecrystallization.

Step 1 was repeated using a 1:1 molar ratio of monoacetate intermediateand 2-carboxy-6-octadecyloxy-lnaphthol and 0.1 equivalent of differentbases as catlysts. The catalysts employed, their pKa'and the percent byweight conversion to dye precursor obtained with each are shown in thefollowing table.

Catalyst pKa Conversion none l 3 chloropyridine 2.84 72Z-aminopyrimidine 3.45 64 ptoluidine 5.08 32 pyridine 5.25 83 a-picoline5.97 79 2,6-lutidine 6.7 73 n-butylamine 10.77 64 triethylamine l l.0l65 di-n-butylamine l 1.25 65 lithium hydride 14. 57

Step 1 also was repeated using different solvents. The substitution ofacetonitrile, t-butanol, dimethoxyethane and a mixture ofacetonitrile-tetrahydrofuran for benzene gave percent by weightconversions to dye precursor or about 80 percent, 70 percent, 80 percentand 80 percent, respectively.

The 3acetoxy-3-( 3 -carbomethoxy-4-hydroxy-1 naphthyl)naphthalideemployed above was prepared as follows:

A mixture of 40.0 g. (0.l mole) of 3-hydroxy-3-(3-carbomethoxy-4-hydroxyl -naphthyl )naphthalide- 1,8, 40 ml. of aceticanhydride (0.43 mole) and 60 ml. of glacial acetic acid was refluxed forabout 2hours with moderate stirring under nitrogen atmosphere. A whitesolid precipitated out of the red homogeneous solution afterapproximately 12 minutes. The reaction mixture was diluted with 200 ml.of a 35 percent solution of hexane in toluene (volume percent). Aftercooling the hexane-toluene suspension to room temperature, an additional150 ml. of 35 percent hexane in toluene was added. The reaction mixturewas cooled in a refrigerator (0 to 5C.) overnight, filtered, washed withthree 100 ml. portions of 35 percent solution of hexane in toluene anddried to give 42.70 (97 percent by weight yield), of the3-acetoxy-naphthalide as a snowwhite solid, melting range 21822C.(dec.).

The preparation of 3-hydroxy-3-(3-carbomethoxy-4-hydroxy-1-naphthyl)naphthalide has been described above. The3-hydroxy-3-(3'-lower carboalkoxy-4'-hydroxy-l'-naphthyl) naphthalidesalso may be synthesized by forming a complex of a l-hydroxy-2- alkylnaphthoate (2-carboxy-l-naphthol) by reacting the naphthoate withanhydrous aluminum chloride followed by the addition of solvent, suchas, nitrobenzene. Naphthalyl dichloride (3.3-dichloronaphthalide) isthen added to the solution containing the naphthoate as an activatedcomplex to form the 3-hydr0xy-(3'- lower carboalkoxy-4-hydroxy-l-naphthyl)naphthalide The l-hydroxy-6-octadecyloxy-2-naphthoic acidemployed in the above Examples was prepared by adding sodium methoxide(67.4 gms., 1,35 mole) to a solution of l,6-dihydroxy-naphthalene (100gms., 0.625 mole) in 900 ml. of dry N,N-dimethyl-formamide saturatedwith dry carbon dioxide gas. A steady flow of carbon dioxide wasmaintained throughout the reaction. Approximately 125 ml. ofdimethylformamide was distilled and the mixture was then refluxed for 15minutes and an additional 125 ml. of solvent removed. The solution wascooled and the flow of carbon dioxide stopped. The reaction mixture wasacidified with concentrated hydrochloric acid and then poured onto about2,000 gms. of ice. The precipitated dark solid was filtered and driedand then triturated with 1 liter of boiling benzene and filtered free ofdark impurities. Recrystallization from water gave 1,6-dihydroxy-2-naphthoic acid as a white solid (melting range 22022lC.). I

5 To a well-stirred slurry of 1,6-dihydroxy-2-naphthoic acid (5.1 gms.,0.025 mole) in 50 ml. of dry isopropyl alcohol under nitrogen was addedpotassium t-butoxide (5.65 gms., 0.050 mole). The mixture was heated toreflux and stirred 10-15 minutes and then octadecyl brolO mide (8.35gms., 0.025 mole) was added. The reaction was refluxed for 5 hours,cooled and acidified with 20 percent hydrochloric acid. The solid whichprecipitated was filtered and dried and recrystallized from absoluteethanol to give 3.8 gms. of grey solid. Further recrystallization fromchloroform gave 2.3 gms.. of lhydroxy-6-octadecyloxy-2-naphthoic acid asa white solid (melting range ,164l65C.).

As noted above, the indicator dyes produced in accordance with thepresent invention are useful as optical filter agents in photographicprocesses, and because of their relatively high pKa, are particularlyuseful in diffusion transfer processes employing highly alkalineprocessing solutions. Their use as optical filter agents in photographicprocesses is disclosed and claimed in copending U. S. patent applicationSer. No. 103,392 of Myron S. Simon and David P. Waller, filed Jan. 4,197 l now U.S. Pat. No. 3,702,245. Certain l-naphthol naphthalidesincluding carboxy-substituted l-naphthol naphthalides form the subjectmatter of copending U.

S. patent application Ser. No. 103,865 of Myron S.

Simon also filed Jan. 4, 197i.

Since certain changes may be made in the above process without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

What is claimed is: l. A method of preparing l-naphthol naphthalideindicator dyes which comprises:

0 A. reacting (a) about 1.0 to L5 moles of a 3-Z- 3( 3'lowercarboalkoxy-4-hydr oxy-l -naphthyl)- naphthalide wherein Z is a leavinggroup and (b) about 1.0 mole of a 2-carboxy-l-naphthol, in an I inertorganic solvent at a temperature not exceeding about 85C. in thepresence of about 0.1 and 2.0 moles of a non-water producing base havinga pKa of not less than about 2 to form the corresponding 3-(3-lowercarboalkoxy-4'-hydroxy-l naphthyl)-3-( 3 -carboxy-4' -hydroxy-lnaphthyl) naphthalide dye precursor and B. hydrolyzing said dyeprecursor to form the corresponding 3-( 3 '-carboxy-4-hydroxy-l-naphthyl)- 3-( 3 -carboxy-4 '-hydroxy-l "-naphthyl )naphthalide dyeproduct.

2. A method as defined in claim 1 wherein said naphthalide (a) is a3-OR-3-(3'-lower carboalkoxy-4'- hydroxy-l '-naphthyl)naphthalidewherein R is a monovalent hydrocarbon radical or a monovalentsubstituted hydrocarbon radical.

3. A method as defined in claim 1 wherein said naphthalide (a) is a3-halo-3-(3'-lower carboalkoxy-4'- hydroxy-l '-naphthyl )naphthalide.

4. A method as defined in claim 1 wherein said base ,5 is pyridine.

5. A method as defined in claim 1 wherein said naphthol (b) is2-carboxy-6-octadecyloxy-l-naphthol.

6. A method as defined in claim wherein said naphv 8. A method asdefined in claim 5 wherein said naphthalide (a) is a 3-OR-3-(3'-lowercarbbalkoxy-4'- thalide (b) is a 3-chl0ro-3-( 3'-l0wer carboalkoxy-4-hydroxy-l -naphthyl)naphthalide wherein R is a phenyl hydroxy-l'-naphthyl )naphthalide. group 7 9. A method as defined in claim 8wherein said naph- 7. A method as defined in claim 6 wherein said naph--5 thalide (b) is 3-chlor0-3-(3-carbomethoxy-4- thalide (b) is3-OR-3-(3-carbomethoxy-4-hydr0xy-l hydroxy-l -naphthyl)naphthalide.naphthyUnaphthalide wherein R is o-hydroxytetrachlorophenyl.

2. A method as defined in claim 1 wherein said naphthalide (a) is a3-OR-3-(3''-lower carboalkoxy-4''-hydroxy-1''-naphthyl)naphthalidewherein R is a monovalent hydrocarbon radical or a monovalentsubstituted hydrocarbon radical.
 3. A method as defined in claim 1wherein said naphthalide (a) is a 3-halo-3-(3''-lowercarboalkoxy-4''-hydroxy-1''-naphthyl)naphthalide.
 4. A method as definedin claim 1 wherein said base is pyridine.
 5. A method as defined inclaim 1 wherein said naphthol (b) is2-carboxy-6-octadecyloxy-1-naphthol.
 6. A method as defined in claim 5wherein said naphthalide (a) is a 3-OR-3-(3''-lowercarboalkoxy-4''-hydroxy-1''-naphthyl)naphthalide wherein R is a phenylgroup.
 7. A method as defined in claim 6 wherein said naphthalide (b) is3-OR-3-(3''-carbomethoxy-4''-hydroxy-1''-naphthyl)naphthalide wherein Ris o-hydroxy-tetrachlorophenyl.
 8. A method as defined in claim 5wherein said naphthalide (b) is a 3-chloro-3-(3''-lowercarboalkoxy-4''-hydroxy-1''-naphthyl)naphthalide.
 9. A method as definedin claim 8 wherein said naphthalide (b) is3-chloro-3-(3''-carbomethoxy-4''-hydroxy-1''-naphthyl)naphthalide.